The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
Traditionally, vehicles include a prime mover, such as an internal combustion engine, that generates drive torque. The drive torque is transferred through a powertrain to drive a drivetrain, propelling the vehicle along a surface. Exemplary powertrain components include a transmission and a coupling device, through which the drive torque from the engine is transferred to the transmission. The transmission multiplies the drive torque by a gear ratio and further transfers the multiplied drive torque to the driveline.
An exemplary transmission includes an automatic transmission having a plurality of transmission elements that are hydraulically engaged to establish a desired gear ratio. Accordingly, each transmission element includes a corresponding hydraulic circuit having a variable bleed solenoid (VBS) to regulate the actuation pressure of a corresponding transmission element, as well as brake switches and pressure switches.
A transmission tie-up condition can occur when a transmission element engages at an inappropriate time. More specifically, in so called clutch to clutch type transmissions, a gear ratio shift is orchestrated by lowering the torque transfer capacity of an off-going (i.e., disengaging) clutch while increasing the torque transfer capacity of an on-coming (i.e., engaging) clutch. In the event that a third or redundant clutch should be applied during steady-state conditions, the vehicle decelerates at a rate that is proportional to the torque transfer capacity that the offending clutch comes on with.
Accordingly, traditional diagnostic routines are implemented in transmission systems to identify the offending clutch upon detection of a tie-up condition. More specifically, traditional diagnostic routines cycle through and diagnose the various control elements (e.g., VBS, pressure switches, brake switches) to identify the offending element and to correct the tie-up condition. These traditional diagnostic routines, however, can result in false detection of tie-up conditions and can induce vibrations or other phenomenon that can be sensed by the driver.